High modulus, nonconductive adhesive useful for installing vehicle windows

ABSTRACT

The invention is a composition comprising
     a) one or more isocyanate functional polyether based prepolymers containing one or more organic based polymers dispersed therein;   b) one or more isocyanate functional polyester based prepolymers which is solid at 23° C.;   c) one or more polyisocyanates having a nominal functionality of about 3 or greater;   d) one or more conductive carbon blacks in an amount such that the composition has a dielectric constant of about 15 or less; and   e) one or more catalysts for the reaction of isocyanate moieties with hydroxyl groups,
 
wherein the composition demonstrates upon cure a modulus of 2.0 MPa or greater at 25° C. measured according to ASTM D4065; a dielectric constant of about 15 or less; a sag of an uncured sample of less than 2 mm, a press flow viscosity of about 20 to about 50 and a storage modulus of about 5.3×10 5  Pa or greater.

FIELD OF INVENTION

The invention relates to a composition useful as an adhesive which isuseful in bonding glass into vehicles and buildings which adhesivedemonstrates high modulus and nonconductive properties. In anotherembodiment, the invention is a method of bonding two or more substratestogether, wherein such substrates may include glass, buildings andvehicles. In another embodiment, the invention is a method of replacinga window in a vehicle using the composition of the invention.

BACKGROUND OF INVENTION

Adhesive compositions are used to affix (bond) glass (windows) intobuildings and vehicles, see Rizk, U.S. Pat. No. 4,780,520; Bhat, U.S.Pat. No. 5,976,305; Hsieh et al, U.S. Pat. No. 6,015,475 and Zhou, U.S.Pat. No. 6,709,539, all incorporated herein by reference. In automobilefactories windows are installed using robots and computer controlledprocessing. This facilitates the use of a variety of high performanceadhesives used on a variety of automobiles, for instance nonconductiveadhesives and high modulus adhesives. Further, new vehicles are notdriven a significant distance for several days after windowinstallation, and thus the speed of cure is not a significant issue.Conversely, when a vehicle needs a window replaced, it is oftenperformed in a remote location by an installer working from a vehicle.In this environment, speed of cure is important as the vehicle ownerdesires to drive the vehicle away as soon as possible after installationon the window. Adhesives useful in replacing windows for vehicles whichfacilitate fast drive away times are known see Bhat, U.S. Pat. No.5,976,305 and Zhou, U.S. Pat. No. 6,709,539. The introduction of varioushigh performance adhesive compositions used for installing windows inautomobile factories presents a problem for replacement windowinstallers. First adhesives that meet all the varied performancerequirements are not available in the market place. Second, it isdifficult to formulate many high performance adhesive compositions toallow rapid drive away times, such as one hour and more preferably 30minutes. Thus, a replacement window installer often has to carry avariety of adhesives so that the installer can match the adhesive to theproperties of the original adhesive. It is also difficult to formulate ahigh performance adhesive that does not sag, that is, lose the shape ofthe adhesive bead applied to the vehicle or the glass.

Adhesives have been developed which provide good initial green strengththat allows the adhesive to hold the glass in place without additionalfixturing to hold the glass in place. This is achieved through theinclusion of crystalline polyesters in the adhesive. These adhesiveshave hot melt properties that require that the adhesive be melted andapplied hot. As the adhesive cools the polyester portion crystallizesand provides initial green strength to hold the glass in place, seeProebster U.S. Pat. No. 5,747,581, incorporated herein by reference. Theproblem with these adhesives is that they require heat to apply and theuse of complex equipment including a heater for their use. The initialgreen strength provided is not sufficient for rapid drive away time. Inthe replacement glass industry segment rapid strength development isnecessary to allow safe rapid drive away times. Because of the use ofhot melt adhesives in the automobile window replacement market, manyinstallers insist on heating adhesives prior to applying the adhesive tothe window or the window flange. Many adhesives when heated demonstratesagging, that is the deformation as the result of gravitational forces.This deformation if severe enough can interfere in the properinstallation and sealing of the window into the vehicle.

Several approaches to providing non-conductive adhesives including usingnon-conductive carbon black in adhesive formulations are known, seecommonly assigned patent application Ser. No. 10/921,635 filed Aug. 19,2004 titled COMPOSITION USEFUL AS AN ADHESIVE FOR INSTALLING VEHICLEWINDOWS. WO 02/053671 discloses the use of low or non-oixidized carbonblack with polycarbonate based polyols to achieve this objective. Theproblem with this technology is that low, conductive carbon black andpolycarbonate polyols are significantly more expensive than standardgrades of carbon black which are conductive.

Windows in buildings and vehicles are installed and replaced in avariety of environmental conditions. Many of the present adhesivecompositions are limited with respect to the environmental conditions ofapplication. As a result window installers often need to use differentadhesives based on the environmental conditions.

What is needed is a composition which is useful as an adhesive forbonding glass into a structure which exhibits a variety of highperformance properties (such as high modulus and nonconductive nature),exhibits fast safe drive away times when applied under a variety ofconditions, fast strength development, can be applied without the needfor heating the adhesive, can be applied under a wide range ofenvironmental conditions, does not require expensive ingredients anddoes not sag when applied. Further, what is needed is an adhesivecomposition which does not sag when heated prior to application totemperatures of up to 80° C.

SUMMARY OF INVENTION

In one embodiment, the invention is a composition comprising

-   a) one or more isocyanate functional polyether based prepolymers    containing one or more organic based polymers dispersed therein;-   b) one or more isocyanate functional polyester based prepolymers    which is solid at 23° C.;-   c) one or more polyisocyanates having a nominal functionality of    about 3 or greater;-   d) one or more conductive carbon blacks in an amount such that the    composition has a dielectric constant of about 15 or less; and-   e) one or more catalysts for the reaction of isocyanate moieties    with hydroxyl groups, wherein the composition demonstrates upon cure    a modulus of about 2.0 MPa or greater at 25° C. measured according    to ASTM D4065; a dielectric constant of about 15 or less; a sag of    an uncured sample of less than about 2 mm, a press flow viscosity of    about 20 to about 50 and a storage modulus of about 5.3×10⁵ Pa or    greater.

In another embodiment the invention is a method of bonding two or moresubstrates together which comprises contacting the two or moresubstrates together with a composition according to this inventiondisposed along at least a portion of the area wherein the substrates arein contact.

In yet another embodiment the invention is a method of replacing awindow of a vehicle comprising

-   i) removing the window from the vehicle;-   ii) applying a composition according to the invention to a    replacement window or to the flange of the vehicle adapted to hold    the window into the vehicle;-   iii) contacting the flange of the vehicle and the replacement window    with the composition disclosed between the replacement window and    the flange of the vehicle; and-   iv) allowing the adhesive to cure.

The composition of the invention is useful as an adhesive to bondsubstrates together. A variety of substrates may be bonded togetherusing the composition, for instance, plastics, glass, wood, ceramics,metal, coated substrates, such as plastics with an abrasion resistantcoating disposed thereon, and the like. The compositions of theinvention may be used to bond similar and dissimilar substratestogether. The compositions are especially useful for bonding glass or aplastic with an abrasion resistant coating disposed thereon to othersubstrates such as vehicles and buildings. The compositions of theinvention are also useful in bonding parts of modular componentstogether, such as vehicle modular components. The glass or plastic withan abrasion resistant coating disposed thereon can be bonded to coatedand uncoated portions of vehicles. Advantageously the adhesive ispumpable, sag resistant and functional, bonds parts together, attemperatures between about 20° C. and about 80° C. This allows theadhesives prepared from the composition of the invention to be appliedat a wide range of ambient temperatures. Heated application machinery isnot necessary for the application of the adhesive. Furthermore, theadhesive demonstrates rapid strength development which facilitates rapiddrive away times of preferably one hour, and more preferably 30 minutes,after application of the adhesive at temperatures of from about 0°F.(−18° C.) to about 115° F. (46° C.). In particular, windshieldsinstalled under such conditions meet United States Federal Motor VehicleSafety Standard (FMVSS) 212. The compositions of the invention arenonconductive and demonstrate a dielectric constant of about 15 or less.The compositions of the invention preferably demonstrate a modulus afterapplication for two weeks of about 2 MPa or greater, more preferablyabout 2.2 MPa or greater and preferably about 3 MPa or less according toASTM D4065. The compositions of the invention exhibit a storage modulus,G′, of about 5.3×10⁵ Pa or greater, preferably about 0.53 MPa or greaterand most preferably about 1.0 MPa or greater. Pumpability of thecomposition can be measured according to the press flow viscosity testdescribed hereinafter; according to that test the composition exhibits apress flow viscosity of about 20 to about 50 seconds.

DESCRIPTION OF FIGURES

FIG. 1 is a graph of conductive carbon percentage versus dielectricconstant.

DETAILED DESCRIPTION OF INVENTION

One or more as used herein means that at least one, or more than one, ofthe recited components may be used as disclosed. Nominal as used withrespect to functionality means the theoretical functionality, generallythis can be calculated from the stoichiometry of the ingredients used.Generally, the actual functionality is different due to imperfections inraw material, incomplete conversion of the reactants and formation ofby-products.

The one or more isocyanate functional polyether based prepolymers arepresent in sufficient quantity to provide adhesive character to thecomposition. Such prepolymers have an average isocyanate functionalitysufficient to allow the preparation of a crosslinked polyurethane uponcure and not so high that the polymers are unstable. Stability in thiscontext means that the prepolymer or adhesive prepared from theprepolymer has a shelf life of at least 6 months at ambienttemperatures, in that it does not demonstrate an increase in viscosityduring such period which prevents its application or use. Preferably theprepolymer or adhesive prepared therefrom does not undergo an increasein viscosity of more than about 50 percent during the stated period. Theprepolymer preferably has a free isocyanate content, which facilitatesacceptable strength in adhesives prepared from the prepolymers after 60minutes and stability of the prepolymer. Preferably, the free isocyanatecontent is about 0.8 percent by weight or greater based on the weight ofthe prepolymer and more preferably about 0.9 percent by weight orgreater, and preferably about 2.2 percent by weight or less, morepreferably about 2.0 or less, even more preferably about 1.4 percent byweight or less and even more preferably about 1.1 percent by weight orless and most preferably about 1.0 percent by weight or less. Aboveabout 2.2 percent by weight the adhesives prepared from the prepolymermay demonstrate lap shear strengths after 60 minutes which are too lowfor the intended use. Below about 0.8 percent by weight the prepolymerviscosity is too high to handle and the working time is too short.

The prepolymer preferably exhibits a viscosity, which facilitatesformulation of a pumpable adhesive which has good green strength.Preferably the viscosity of the prepolymer is about 100,000 centipoise(100 Pa s) or less and more preferably about 70,000 centipoise (70 Pas)) or less, and most preferably about 45,000 centipoise (45 Pa s) orless and about 30,000 centipoise (30 Pa s) or greater. The viscosityused herein is Brookfield viscosity determined using a number 5 spindle.The viscosity of the adhesive can be adjusted with fillers, although thefillers generally do not improve the green strength of the finaladhesive. Below about 30,000 centipoise (30 Pa s) the adhesive preparedfrom the prepolymer may exhibit poor green strength. Above about 100,000(100 Pa s) the prepolymer may be unstable and hard to dispense. Theprepolymer may be prepared by any suitable method, such as by reactingpolyols, such as diols, triols and dispersion triols such as a copolymerpolyol or grafted triol, with an excess over stoichiometry of one ormore polyisocyanates under reaction conditions sufficient to form aprepolymer having isocyanate functionality and free isocyanate contentwhich meets the criteria discussed above. In a preferable method used toprepare the prepolymer, the polyisocyanates are reacted with one or morediols, one or more triols and one or more dispersion triols.

Preferable polyisocyanates for use in preparing the prepolymer includethose disclosed in U.S. Pat. No. 5,922,809 at column 3, line 32 tocolumn 4, line 24 incorporated herein by reference. Preferably thepolyisocyanate is an aromatic or cycloaliphatic polyisocyanate such asdiphenylmethane-4,4′-diisocyanate, isophorone diisocyanate,tetramethylxylene diisocyanate, and is most preferablydiphenylmethane-4,4′-diisocyanate. The diols and triols are genericallyreferred to as polyols. Polyols useful in this invention are diols andtriols corresponding to the polyols described in U.S. Pat. No. 5,922,809at column 4, line 60 to column 5, line 50, incorporated herein byreference. Preferably the polyols (diols and triols) are polyetherpolyols and more preferably polyoxyalkylene oxide polyols. Mostpreferred triols are ethylene oxide-capped polyols prepared by reactingglycerin with propylene oxide, followed by reacting the product withethylene oxide.

Preferably the prepolymer contains one or more organic based polymersdispersed therein. Preferably the organic based polymer is included inthe prepolymer by inclusion of a dispersion triol having dispersedtherein particles of an organic based polymer. The preferable dispersiontriols are disclosed in Zhou, U.S. Pat. No. 6,709,539 at column 4, line13 to column 6, line 18, incorporated herein by reference. Preferablythe triol used to disperse the organic particles is a polyether trioland more preferably a polyoxyalkylene based triol. Preferably, suchpolyoxyalkylene oxide triol comprises a polyoxypropylene chain with apolyoxyethylene end cap. Preferably the triols used have a molecularweight of about 4,000 or greater, more preferably about 5,000 or greaterand most preferably about 6,000 or greater. Preferably such triol hasmolecular weight of about 8,000 or less and more preferably about 7,000or less.

Preferably the particles dispersed in the dispersion triol comprise athermoplastic polymer, rubber-modified thermoplastic polymer or apolyurea dispersed in a triol. The polyurea preferably comprises thereaction product of a polyamine and a polyisocyanate. Preferablethermoplastic polymers are those based on monovinylidene aromaticmonomers and copolymers of monovinylidene aromatic monomers withconjugated dienes, acrylates, methacrylates, unsaturated nitrites ormixtures thereof. The copolymers can be block or random copolymers. Morepreferably the particles dispersed in the triol comprise copolymers ofunsaturated nitrites, conjugated dienes and a monovinylidene aromaticmonomer, a copolymer of an unsaturated nitrile and a monovinylidenearomatic monomer or a polyurea. Even more preferably the particlescomprise a polyurea or polystyrene-acrylonitrile copolymer with thepolystyrene-acrylonitrile copolymers being most preferred. The organicpolymer particles dispersed in the triol preferably have a particle sizewhich is large enough to improve the impact properties and elastomericproperties of the finally cured adhesive, but not so large so as toreduce the ultimate strength of the adhesive after cure. The particlesmay be dispersed in the triol or grafted to the backbone of some of thetriols. Preferably the particle size is about 10 microns or greater andmore preferably the particle size is about 20 microns or greater.Preferably the particle size is about 50 microns or less and morepreferably the particle size is about 40 microns or less. The trioldispersion contains a sufficient amount of organic polymer particlessuch that the adhesive upon cure has sufficient hardness for the desireduse and not so much such that the cured adhesive has too much elasticityas defined by elongation. Preferably the dispersion contains about 20percent by weight or greater of organic polymer particles copolymerbased on the dispersion, preferably about 30 percent by weight orgreater and more preferably about 35 percent by weight or greater.Preferably the dispersion contains about 60 percent by weight or less oforganic polymer particles based on the dispersion, preferably about 50percent by weight or less and more preferably about 45 percent by weightor less.

The polyols (diols and triols and dispersion triols) are present in anamount sufficient to react with most of the isocyanate groups of theisocyanates leaving enough isocyanate groups to correspond with thedesired free isocyanate content of the prepolymer. Preferably thepolyols are present in an amount of about 30 percent by weight orgreater based on the prepolymer, more preferably about 40 percent byweight or greater and most preferably about 55 percent by weight orgreater. Preferably the polyols are present in an amount of about 75percent by weight or less based on the prepolymer, more preferably about65 percent by weight or less and most preferably about 60 percent byweight or less.

The weight ratio of diols to triols and dispersion triols is importantto achieving the desired cure rate and strength of the adhesive. If theweight ratio is too low the formulation is too viscous to handle and theresulting adhesive has insufficient elasticity to retain glass in anautomobile window frame under crash conditions. If the ratio is too highthe adhesive does not have adequate green strength. The weight ratio ofdiol to triol and dispersion triol is preferably about 0.8 or greaterand more preferably about 0.85 or greater and most preferably about 0.9or greater. The weight ratio of diol to triol and dispersion triol isabout 1.2 or less; more preferably about 1.0 or less and most preferablyabout 0.95 or less. In the embodiment where the polyols comprise amixture of diols and triols, the amount of diols present is preferablyabout 15 percent by weight or greater based on the prepolymer, morepreferably about 25 percent by weight or greater and most preferablyabout 28 percent by weight or greater; and about 40 percent by weight orless based on the prepolymer, more preferably about 35 percent by weightor less and most preferably about 30 percent by weight or less. In theembodiment where the polyols comprise a mixture of diols and triols, theamount of triols (non dispersion triol and dispersion triol) present ispreferably about 15 percent by weight or greater based on theprepolymer, more preferably about 25 percent by weight or greater andmost preferably about 28 percent by weight or greater; and preferablyabout 45 percent by weight or less based on the prepolymer, morepreferably about 35 percent by weight or less and most preferably about32 percent by weight or less.

The dispersion of organic polymer particles in a triol is present in theprepolymer in an amount of about 10 percent by weight or greater of theprepolymer and more preferably about 12 percent by weight or greater,and about 18 percent by weight or less of the prepolymer and morepreferably about 15 percent by weight or less.

The polyurethane prepolymers of the invention may further comprise aplasticizer. The plasticizers useful in the prepolymer are commonplasticizers useful in polyurethane adhesive applications and well knownto those skilled in the art. The plasticizer is present in an amountsufficient to disperse the prepolymer in the final adhesive composition.The plasticizer can be added to the adhesive either during preparationof the prepolymer or during compounding of the adhesive composition.Preferably the plasticizer is present in about 1 percent by weight orgreater of the prepolymer formulation (prepolymer plus plasticizer),more preferably about 20 percent by weight or greater and mostpreferably about 30 percent by weight or greater. Preferably theplasticizer is present in about 45 percent by weight or less of theprepolymer formulation and more preferably about 35 percent by weight orless.

The polyurethane prepolymer may be prepared by any suitable method, suchas bulk polymerization and solution polymerization. Preferable processesfor the preparation of the prepolymers are disclosed in U.S. Pat. No.5,922,809 at column 9, line 4 to 51 incorporated herein by reference.The polyurethane prepolymers are present in the adhesive composition inan amount sufficient such that when the resulting adhesive curessubstrates are bound together. Preferably the polyurethane prepolymersare present in an amount of about 25 parts by weight of the adhesivecomposition or greater, more preferably about 30 parts by weight orgreater and most preferably about 35 parts by weight or greater.Preferably, the polyurethane prepolymers are present in an amount ofabout 55 parts by weight of the adhesive composition or less, morepreferably about 50 parts by weight or less and even more preferablyabout 45 parts by weight or less.

The composition further comprises one or more isocyanate functionalprepolymers containing one or more polyester based polyols which aresolid at ambient temperature, about 23° C. The polyester based polyolshave melting points such that the prepolymer provides sufficient greenstrength to prevent the substrates from moving in relation to oneanother due to gravitational forces and such that the prepolymer issolid at ambient temperatures. In terms of installing a window in avehicle or building, the polyester based prepolymer prevents the windowfrom sliding after installation. In one embodiment, the one or moreisocyanate functional polyester based prepolymers are present in anamount of about 0.5 to about 10 percent based on the weight of thecomposition. Preferably, the polyester polyols have melting points ofabout 40° C. or greater, even more preferably about 45° C. or greaterand most preferably about 50° C. or greater. Preferably, the polyesterpolyols exhibit melting points of about 85° C. or less and mostpreferably about 60° C. or less and even more preferably about 70° C. orless. The polyester based isocyanate prepolymer can be prepared usingone or more polyester polyols. The amount of polyester polyol in theprepolymer is a sufficient amount to provide the needed green strengthto the composition of the invention and to render it solid. Preferably,the polyester polyol is present in the polyester polyol based isocyanateprepolymer in an amount of about 70 percent by weight or greater basedon the weight of the prepolymer and more preferably about 80 percent byweight or greater. Preferably, the polyester polyol is present in thepolyester polyol based isocyanate prepolymer in an amount of about 95percent by weight or less based on the weight of the prepolymer and morepreferably about 90 percent by weight or less. Preferably, the polyesterpolyol based isocyanate prepolymer is present in the adhesivecomposition in sufficient amount to give the needed green strength andthe desired rheology of the composition. Preferably, the polyesterpolyol based isocyanate prepolymer is present in the adhesivecomposition in an amount of about 1 percent by weight or greater basedon the weight of the prepolymer and most preferably about 2 percent byweight or greater. Preferably, the polyester polyol based isocyanateprepolymer is present in the adhesive composition in an amount of about5 percent by weight or less and most preferably about 3 percent byweight or less. The polyester polyol can be any polyester compositionthat meets the property requirements defined, which is crystalline atambient temperatures and melts in the desired temperature range.Preferred polyester polyols are prepared from linear diacids and lineardiols. A more preferred diacid is adipic acid. More preferred diols arethe C₂₋₆ diols, with butane diols, pentane diols and hexane diols beingmost preferred. The polyester based polyisocyanate prepolymers can beprepared using the processes and isocyanates described hereinbefore.Preferred polyester polyols are available from Creanova under the tradename Dynacol and the designations 7360 and 7330, with 7360 morepreferred.

The composition of the invention further comprises a polyfunctionalisocyanate for the purpose of improving the modulus of the compositionin the cured form. Polyfunctional as used in the context of theisocyanates refers to isocyanates having a functionality of 3 orgreater. The polyisocyanates can be any monomeric, oligomeric orpolymeric isocyanate having a nominal functionality of about 3 orgreater. More preferably the polyfunctional isocyanate has a nominalfunctionality of about 3.2 or greater. Preferably the polyfunctionalisocyanate has a nominal functionality of about 5 or less, even morepreferably about 4.5 or less and most preferably about 4.2 or less. Thepolyfunctional isocyanate can be any isocyanate which is reactive withthe isocyanate polyisocyanate prepolymers used in the composition andwhich improves the modulus of the cured composition. The polyisocyanatescan be monomeric; trimers, isocyanurates or biurets of monomericisocyanates; oligomeric or polymeric, the reaction product of severalunits of one or more monomeric isocyanates. Examples of preferredpolyfunctional isocyanates include trimers of hexamethylenediisocyanate, available from Bayer under the trademark and designationDesmodur® N3300, and polymeric isocyanates such as polymeric MDI(methylene diphenyl diisocyanates) such as those marketed by The DowChemical Company under the trademark of PAPI™ including PAPI™ 20polymeric isocyanate. The polyfnctional isocyanates are present insufficient amount to impact the modulus of the cured compositions of theinvention. If too much is used the cure rate of the composition isunacceptably slowed down. If too little is used the desired moduluslevels are not achievable. The polyfunctional isocyanate is preferablypresent in an amount of about 0.5 percent by weight or greater based onthe weight of the composition, more preferably about 1.0 percent byweight or greater and most preferably about 1.4 percent by weight orgreater. The polyfunctional isocyanate is preferably present in anamount of about 8 percent by weight or less, based on the weight of thecomposition, more preferably about 5 percent by weight or less and mostpreferably about 2.5 percent by weight or less.

The composition of the invention also comprises carbon black to give thecomposition the desired black color, viscosity and sag resistance. Oneor more carbon blacks may be used in the composition. The carbon blackused in this invention may be a standard carbon black which is notspecially treated to render it nonconductive. Standard carbon black iscarbon black which is not specifically surface treated or oxidized. Oneor more nonconductive carbon blacks may be used in conjunction with thestandard carbon black, although such inclusion may add unnecessarycosts. The amount of standard carbon black in the composition is thatamount which provides the desired color, viscosity, sag resistance andprovided the composition is nonconductive to the level defined herein.The standard carbon black is preferably used in the amount of about 10percent by weight or greater based on the weight of the composition,more preferably about 12 percent by weight or greater and mostpreferably about 14 percent by weight or greater. The standard carbonblack is preferably present in an amount of about 20 percent by weightor less based on the weight of the composition, more preferably about 18percent by weight or less and most preferably about 16 percent by weightor less. The total carbon black present including conductive or standardand non-conductive carbon black is preferably about 35 percent by weightor less based on the weight of the composition, more preferably about 30percent by weight or less and most preferably about 20 percent by weightor less. Standard carbon blacks are well known in the art and includeRaven™ 790, Raven™ 450, Raven™ 500, Raven™ 430, Raven™ 420 and Raven™410 carbon blacks available from Colombian and CSX™ carbon blacksavailable from Cabot, and Printex™30 carbon black available fromDegussa. Nonconductive carbon blacks are well known in the art andinclude Raven™ 1040 and Raven™ 1060 carbon black available fromColombian.

The adhesive composition of the invention may further comprise acatalyst known for promoting the cure of polyurethanes in the presenceof moisture. Preferable catalysts include metal salts such as tincarboxylates, organo titanates (such as alkyl titanates), metalcarboxylates, tertiary amines, such as dimorpholinodiethyl ether oralkyl-substituted dimorpholinodiethyl ethers. In one embodiment one ormore catalysts for the reaction of isocyanate moieties with hydroxylgroups are present in an amount of about 0.005 to about 2 percentwherein the percentages are based on the weight of the composition.Preferably, the catalyst comprises a mixture of metal carboxylates andone of dimorpholino-diethyl ether or an alkyl substituted dimorpholinodiethyl ether. Preferred metal carboxylates include bismuthcarboxylates. Among preferred catalysts are bismuth octoate,dimorpholinodiethyl ether and(di-(2-(3,5-dimethylmorpholino)ethyl))ether. Such catalysts, whenemployed are preferably employed in an amount based on the weight of theadhesive composition of about 0 parts by weight or greater, morepreferably about 0.1 parts by weight or greater, even more preferablyabout 0.2 parts by weight or greater and most preferably about 0.4 partsby weight or greater. Such catalysts are preferably employed in anamount, based on the weight of the adhesive composition of about 5 partsby weight or less, more preferably about 1.75 parts by weight or less,even more preferably about 1 part by weight or less and most preferablyabout 0.6 parts by weight or less.

The adhesive of the invention may be formulated with fillers andadditives known in the prior art for use in adhesive compositions. Bythe addition of such materials physical properties such as viscosityflow rates and the like can be modified. However, to prevent prematurehydrolysis of the moisture sensitive groups of the polyurethaneprepolymer, fillers should be thoroughly dried before admixturetherewith.

Optional components of the adhesive of the invention include reinforcingfillers. Such fillers are well known to those skilled in the art andinclude carbon black, titanium dioxide, calcium carbonate, surfacetreated silicas, titanium oxide, fume silica, talc, and the like.Preferred reinforcing fillers comprise carbon black as describedhereinbefore. In one embodiment, more than one reinforcing filler may beused, of which one is carbon black. The reinforcing fillers are used insufficient amount to increase the strength of the adhesive and toprovide thixotropic properties to the adhesive.

Among optional materials in the adhesive composition are clays.Preferred clays useful in the invention include kaolin, surface treatedkaolin, calcined kaolin, aluminum silicates and surface treatedanhydrous aluminum silicates. The clays can be used in any form, whichfacilitates formulation of a pumpable adhesive. Preferably the clay isin the form of pulverized powder, spray-dried beads or finely groundparticles. Clays may be used in an amount of about 0 parts by weight ofthe adhesive composition or greater, more preferably about 1 part byweight or greater and even more preferably about 6 parts by weight orgreater. Preferably the clays are used in an amount of about 25 parts byweight or less of the adhesive composition and more preferably about 10parts by weight or less.

The adhesive composition of this invention may further compriseplasticizers so as to modify the Theological properties to a desiredconsistency. Such materials should be free of water, inert to isocyanategroups and compatible with a polymer. Suitable plasticizers are wellknown in the art and preferable plasticizers include alkyl phthalatessuch as dioctylphthalate or dibutylphthalate, partially hydrogenatedterpene commercially available as “HB-40”, trioctyl phosphate, epoxyplasticizers, toluene-sulfamide, chloroparaffins, adipic acid esters,castor oil, toluene and alkyl naphthalenes. The amount of plasticizer inthe adhesive composition is that amount which gives the desiredrheological properties and which is sufficient to disperse the catalystin the system. The amounts disclosed herein include those amounts addedduring preparation of the prepolymer and during compounding of theadhesive. Preferably plasticizers are used in the adhesive compositionin an amount of about 0 parts by weight or greater based on the weightof the adhesive composition, more preferably about 5 parts by weight orgreater, more preferably about 10 parts by weight or greater and mostpreferably about 15 parts by weight or greater. The plasticizer ispreferably used in an amount of about 40 parts by weight or less basedon the total amount of the adhesive composition, more preferably about30 parts by weight or less and most preferably about 25 parts by weightor less.

The composition of this invention may further comprise stabilizers,which function to protect the adhesive composition from moisture,thereby inhibiting advancement and preventing premature crosslinking ofthe isocyanates in the adhesive formulation. Stabilizers known to theskilled artisan for moisture curing adhesives may be used preferablyherein. Included among such stabilizers are diethylmalonate, alkylphenolalkylates, paratoluene sulfonic isocyanates, benzoyl chloride andorthoalkyl formates. Such stabilizers are preferably used in an amountof about 0.1 parts by weight or greater based on the total weight of theadhesive composition, preferably about 0.5 parts by weight or greaterand more preferably about 0.8 parts by weight or greater. Suchstabilizers are used in an amount of about 5.0 parts by weight or lessbased on the weight of the adhesive composition, more preferably about2.0 parts by weight or less and most preferably about 1.4 parts byweight or less.

The composition of this invention may further comprise an adhesionpromoter, such as those disclosed in Mahdi, US Patent Publication2002/0100550 paragraphs 0055 to 0065 and Hsieh, U.S. Pat. No. 6,015,475column 5 line 27 to Column 6, line 41 incorporated herein by reference.The amounts of such adhesion promoters useful are also disclosed inthese references and incorporated herein by reference.

The adhesive composition may further comprise a hydrophilic materialthat functions to draw atmospheric moisture into the composition. Thismaterial enhances the cure speed of the formulation by drawingatmospheric moisture to the composition. Preferably, the hydrophilicmaterial is a liquid. Among preferred hydroscopic materials arepyrolidinones such as 1 methyl-2-pyrolidinone, available from under thetrademark m-pyrol. The hydrophilic material is preferably present in anamount of about 0.1 percent by weight or greater and more preferablyabout 0.3 percent by weight or greater and preferably about 1.0 percentby weight or less and most preferably about 0.6 percent by weight orless. Optionally the adhesive composition may further comprise athixotrope. Such thixotropes are well known to those skilled in the artand include alumina, limestone, talc, zinc oxides, sulfur oxides,calcium carbonate, perlite, slate flour, salt (NaCl), cyclodextrin andthe like. The thixotrope may be added to the adhesive of composition ina sufficient amount to give the desired rheological properties.Preferably, the thixotrope is present in an amount of about 0 parts byweight or greater based on the weight of the adhesive composition,preferably about 1 part by weight or greater. Preferably, the optionalthixotrope is present in an amount of about 10 parts by weight or lessbased on the weight of the adhesive composition and more preferablyabout 2 parts by weight or less.

Other components commonly used in adhesive compositions may be used inthe adhesive composition of this invention. Such materials are wellknown to those skilled in the art and may include ultravioletstabilizers and antioxidants and the like.

As used herein all parts by weight relative to the components of theadhesive composition are based on 100 total parts by weight of theadhesive composition.

The adhesive composition of this invention may be formulated by blendingthe components together using means well known in the art. Generally,the components are blended in a suitable mixer. Such blending ispreferably conducted in an inert atmosphere in the absence of oxygen andatmospheric moisture to prevent premature reaction. It may beadvantageous to add any plasticizers to the reaction mixture forpreparing the isocyanate containing prepolymer so that such mixture maybe easily mixed and handled. Alternatively, the plasticizers can beadded during blending of all the components. Once the adhesivecomposition is formulated, it is packaged in a suitable container suchthat it is protected from atmospheric moisture and oxygen. Contact withatmospheric moisture and oxygen could result in premature crosslinkingof the polyurethane prepolymer-containing isocyanate groups.

The adhesive composition of the invention is used to bond a variety ofsubstrates together as described hereinbefore. The composition can beused to bond porous and nonporous substrates together. The adhesivecomposition is applied to a substrate and the adhesive on the firstsubstrate is thereafter contacted with a second substrate. In preferredembodiments, the surfaces to which the adhesive is applied are cleanedand primed prior to application, see for example, U.S. Pat. Nos.4,525,511; 3,707,521 and 3,779,794; relevant parts of all areincorporated herein by reference. Generally the adhesives of theinvention are applied at ambient temperature in the presence ofatmospheric moisture. Exposure to atmospheric moisture is sufficient toresult in curing of the adhesive. Curing can be accelerated by theaddition of additional water or by applying heat to the curing adhesiveby means of convection heat, microwave heating and the like. Preferablythe adhesive of the invention is formulated to provide a working time ofabout 6 minutes or greater more preferably about 10 minutes or greater.Preferably the working time is about 15 minutes or less and morepreferably about 12 minutes or less.

The adhesive composition is preferably used to bond glass or plasticcoated with an abrasion resistant coating, to other substrates such asmetal or plastics. In a preferred embodiment the first substrate is aglass, or plastic coated with an abrasion resistant coating, window andthe second substrate is a window frame. In another preferred embodimentthe first substrate is a glass, or plastic coated with an abrasionresistant coating, window and the second substrate is a window frame ofan automobile. Preferably, the glass window is cleaned and has a glassprimer applied to the area to which the adhesive is to be bonded. Theplastic coated with an abrasion resistant coating can be any plasticwhich is clear, such as polycarbonate, acrylics, hydrogenatedpolystyrene or hydrogenated styrene conjugated diene block copolymershaving greater than 50 percent styrene content. The coating can compriseany coating which is abrasion resistant such as a polysiloxane coating.Preferably, the coating has an ultraviolet pigmented light blockingadditive. Preferably, the glass or plastic window has an opaque coatingdisposed in the region to be contacted with the adhesive to block UVlight from reaching the adhesive.

In a preferred embodiment the composition of the invention is used toreplace windows in structures or vehicles and most preferably invehicles. The first step is removal of the previous window. This can beachieved by cutting the bead of the adhesive holding the old window inplace and then removing the old window. Thereafter the new window iscleaned and primed. The old adhesive that is located on the windowflange can be removed, although it is not necessary and in most cases itis left in place. The window flange is preferably primed with a paintprimer. The adhesive is applied in a bead to the periphery of the windowlocated such that it will contact the window flange when placed in thevehicle. The window with the adhesive located thereon is then placedinto the flange with the adhesive located between the window and theflange. The adhesive bead is a continuous bead that functions to sealthe junction between the window and the window flange. A continuous beadof adhesive is a bead that is located such that the bead connects ateach end to form a continuous seal between the window and the flangewhen contacted. Thereafter the adhesive is allowed to cure.

In another embodiment the compositions of the invention can be used tobond modular components together. Examples of modular components includevehicle modules, such as door, window or body.

Viscosities as described herein are determined according to theprocedure disclosed in Bhat, U.S. Pat. No. 5,922,809 at column 12 lines38 to 49, incorporated herein by reference.

Molecular weights as described herein are determined according to thefollowing to the procedure disclosed in Bhat U.S. Pat. No. 5,922,809 atcolumn 12 lines 50 to 64, incorporated herein by reference.

In reference to polyurethane prepolymers, average isocyanatefunctionality is determined according to the procedure disclosed inBhat, U.S. Pat. No. 5,922,809 at column 12 lines 65 to Column 13, line26, incorporated herein by reference.

ILLUSTRATIVE EMBODIMENTS OF THE INVENTION

The following examples are provided to illustrate the invention, but arenot intended to limit the scope thereof All parts and percentages are byweight unless otherwise indicated.

Preparation of Polyether Prepolymer

A polyether polyurethane prepolymer was prepared by mixing 980 g of apolyoxypropylene diol having an average molecular weight of 2,000 with595 g of a polyoxypropylene triol having an average molecular weight of4500 and 455 g of a styrene acrylonitrile dispersed polyoxypropylenetriol with an average molecular weight of 5400. Mixing was carried outin a reactor by heating the mixture to 48° C. 320 g ofdipheylmethane-4,4′-diisocyanate and 0.17 g of stannous octoate wereadded to the mixture. The whole mixture was then reacted for one hour at80° C. Finally, 1120 g of a dialkyl phthalate plasticizer was added tothe mixture and the mixing was continued for one hour.

Preparation of Polyester Prepolymer 1

A polyester polyurethane prepolymer was prepared by charging 150 g ofdiphenylmethane-4,4′-diisocyanate (MDI) to a reaction vessel and heatingto 48° C. Then 850 g of molten linear polyester diol (Dynacoll 7360) wasslowly added and allowed to react for thirty minutes with a maximumallowable temperature of 88° C.

Preparation of Polyester Prepolymer 2

A polyester polyurethane prepolymer was prepared by charging 175 g of adialkyl phthalate plasticizer to a reaction vessel and heating to 48° C.To this 108 g of diphenylmethane-4,4′-diisocyanate was added and mixedto insure that the MDI was molten. Then 717 g of molten linearcopolyester diol (Dynacoll 7330) was slowly added and allowed to reactfor thirty minutes. The maximum temperature allowed is 88° C. Thepolyester used demonstrated a melting point of 80-85° C.

Compounding of Adhesives

All of the adhesives were made according to the following compoundingprocedure using the raw material percentages listed in Table 1 below.The only change between the different formulations is the compoundingtemperature. Adhesives without the polyester prepolymers were compoundedat room temperature; otherwise, the mixing vessel was heated to 55° C.for the polyester polyurethane prepolymers.

The mixing vessel was heated to the desired temp if the polyesterpolyurethane prepolymer were used. The appropriate amounts of polyetherprepolymer and multifunctional isocyanate (Desmodur® N3300 or PAPI™2020) were charged to the vessel and degassed under vacuum for 15minutes. The polyester polyurethane prepolymers were then added and thematerials were degassed under vacuum for an additional 15 minutes. Thecarbon black and clay fillers were added and mixed for five minutes atslow speed under vacuum until the fillers were sufficiently wetted bythe prepolymers. The mixing speed was increased and the fillersdispersed for 20 minutes. Finally, the dimorpholino diethyl ether andbismuth octoate catalysts and the N-methyl pyrolidone were added to themixing vessel and the mixture was mixed under vacuum for an additional10 minutes.

Testing Procedures

G-Modulus: The shear modulus of the fully cured adhesives was determinedby Instron at 10 percent and 20 percent strain. A lap shear sample wasmade with 5 mm×10 mm×1 mm dimension and fully cured prior to testing.

Storage Modulus (Green Strength) at Short Cure Times: The storagemodulus of the adhesives was determined at short cure times through theuse of a Dynamic Stress Rheometer (DSR). The DSR was programmed to applya stress at a frequency of five rad/sec using 8 mm parallel plategeometry with a plate separation height of 1 mm. The adhesive sample wasapplied to the plates and the storage modulus was recorded every 2minutes for the first two hours after dispensing at the indicatedtemperatures.

High Temperature Sag Test: An 8 mm by 12 mm isosceles triangle bead ofthe adhesive is dispensed with a standard caulking gun onto a surfaceheld at a 60° angle from horizontal. Acceptable performance is a minimaldeflection of the bead tip; no defection or change in shape ispreferred. The test used was conducted on the adhesives after aging for10 hours at 80° C. The adhesives were dispensed while still hot at 80°C. and the amount of sag was recorded as the number of mm of deflectionof the bead tip.

Press Flow Viscosity: The press flow viscosity is determined as the time(seconds) required to extrude 20 grams of adhesive through a capillary.The width of the capillary is fixed at 0.203 in (5.1 mm) and the appliedpressure is 80 psi (5.5×10⁵ Pa). Unless otherwise noted, all press flowviscosity values were determined at 23+/−1° C.

Results

The dielectric constant of the fully cured adhesive was determined byusing a Hewlett Packard 4396A Network/Spectrum Analyzer PC, as per DIN53482 test.

Table 1 describes the formulations tested and the results.

The tested adhesives can be dispensed at room temperature (typicallydemonstrating a press flow viscosity range of between 20 and 50 secondsfor materials that will be applied with a caulking gun).

TABLE 1 Example 1* 2 Polyether based prepolymer containing 66 58.86 30percent plasticizer Desmodur ® N3300 polyfunctional isocyanate 1.5 0PAPI ® 20 polyfunctional isocyanate 0 1.3 DMDEE 0.34 0.34 BismuthOctoate 0.2 0.2 M-Pyrol 0.3 0.3 Clay 10.66 21.5 Raven 790 StandardCarbon Black 0 16 Raven 1040 Nonconductive Carbon Black 16 0 Polyesterbased prepolymer 1 3 1.5 Polyester based prepolymer 2 2 0 Total 100 100G-Modulus (MPa) 2.21 2.19 Dielectric Constant 11 12.5 Rheology (80° C.hot sag) 1 mm 0 Green Strength G′ (pa) by DSR @23° Time (hour) 03.45E+04 1.83E+05 0.5 5.46E+04 5.38E+05 1 8.70E+04 9.32E+05 1.5 1.35E+051.38E+06 2 1.99E+05 1.78E+06 *Comparative Example DMDEE is dimorpholinodiethyl ether

Table 2 Illustrates formulations made as described by Example 2 abovewith different carbon black formulations.

TABLE 2 Dielectric Rheology Example Carbon Black Constance (80° C. hotsag) 3 Raven 790 12.48 0 4 Standard Cabot Carbon Black 10.83 0 5Standard Cabot Carbon Black 12.11 0 6 Printex 30 13.06 0 7 Raven 652A10.2 0 8 Raven 450 5.45 0 9 Raven 500 8.23 0 10 Raven 430 6.19 0 11Raven 420 7.12 4 mm 12 Raven 410 5.36 4 mm

The sag performance of examples 3-10 is excellent, the carbons used hadthe properties of Oil Absorption Number (OAN) of 60 or greater, andsurface area of 31 m²/g or greater. The low conductivity requirement isdemonstrated by each of these adhesives by demonstrating a dielectricconstant of less than 15.

Table 3 demonstrates dielectric constant versus carbon black levelsused. Cabot Carbon was used in Examples 13-19. The data shows that thedielectric constant increases with the increased amount of carbon usage.The adhesives meet low conductive specification when conductive carbonis used at 20 percent or less and demonstrate excellent rheologyproperties. FIG. 1 presents the data of Table 3 in graphic form whichgraphs the percent carbon black verses the dielectric constant.

Carbon Dielectric G-Modulus Rheology Example Black % Constance (MPa) @10% (80° C. hot sag) 13 12 8.7 2.12 0 14 14 9.78 2.2 0 15 16 10.2 2.4 016 18 11.34 2.6 0 17 20 14.16 2.69 0  18* 22 15.57 2.94 0  19* 24 20.483.14 0 Comparative

1. A composition comprising: a) from about 25 to about 55 percent of oneor more isocyanate functional polyether based prepolymers containing oneor more organic based polymers dispersed therein having a freeisocyanate content of about 0.8 to about 2.2 percent by weight based onthe weight of the prepolymer; b) from about 0.5 to about 10 percent ofone or more isocyanate functional polyester based prepolymers which issolid at 23° C.; c) from about 1 to about 8 percent of one or morepolyisocyanates having a nominal functionality of about 3 or greater; d)from about 10 to about 18 percent of one or more conductive carbonblacks in an amount such that the composition has a dielectric constantof about 15 or less; and e) from about 0.005 to about 2 percent one ormore catalysts for the reaction of isocyanate moieties with hydroxylgroups; wherein the percentages are based on the weight of thecomposition and the composition demonstrates upon cure a modulus of 2.0MPa or greater at 25° C. measured according to ASTM D4065; a dielectricconstant of about 15 or less; a sag of an uncured sample of less than 2mm, a press flow viscosity of about 20 to about 50 and a storage modulusof about 5.3×10⁵ Pa or greater.
 2. A composition according to claim 1wherein the isocyanate functional polyester prepolymer exhibits amelting point of about 50° C. or greater.
 3. A composition according toclaim 2 wherein the polyfunctional polyisocyanate is an oligomer orpolymer based on hexamethylene diisocyanate or methylene diphenyldiisocyanate.
 4. A composition according to claim 1 wherein the organicbased polymer is a thermoplastic polymer, a rubber modifiedthermoplastic polymer or a polyurea.
 5. A composition according to claim4 wherein the organic based polymer is a rubber modified thermoplasticpolymer.
 6. A composition according to claim 1 wherein a) the one ormore isocyanate functional polyether based prepolymers are present in anamount of about 25 to about 55 percent; b) the one or more isocyanatefunctional polyester based prepolymers are present in an amount of about1 to about 5 percent; c) one or more polyfunctional isocyanates arepresent in an amount of about 1 to about 8 percent; d) one or moreconductive carbon blacks are present in an amount of about 10 to about18 percent; and e) one or more catalysts for the reaction of isocyanatemoieties with hydroxyl groups are present in an amount of about 0.1 toabout 1.75 percent; wherein the percentages are based on the weight ofthe composition.